Methods for deactivating metallic catalyst residues in polyester and polyester-polycarbonate compositions are known in the art; however, it is desirable to find improved methods for deactivating such residues. It is also desirable to find methods for deactivating catalyst residues that provide compositions with greater hydrolytic stability, that are less detrimental to process equipment, provide better color, and less batch-to-batch variation in color.
It is known in the art that certain phosphorus-containing compounds are useful for deactivating metallic catalysts residues. Reference is made, for example, to U.S. Pat. No. 3,218,372 (Okamura et al.), U.S. Pat. No. 4,532,290 (Jaquiss et al.), U.S. Pat. No. 4,088,709 (Seymour et al.), U.S. Pat. No. 4,401,804 (Wooten et al.), U.S. Pat. No. 5,922,816 (Hamilton) and European Patents 0543125 (Van Helmond), 0294862 (Verhoeven), 0295730 (Verhoeven). Examples of such phosphorus-containing compounds include phosphoric acid, certain organic phosphorus compounds such as distearylpentaerythritol diphosphite, mono-, di-, and trihydrogen phosphate compounds, or di- and triester phosphate compounds, phosphite compounds, certain inorganic phosphorus compounds such as monosodium phosphate, zinc or calcium phosphates, poly(ethylene)hydrogen phosphate, phosphites and phosphates used in combination with elementary sulfur, silyl phosphates, phosphorus compounds used in combinations with metal sulphides or metal sulphates. U.S. Pat. No. 4,452,933 (Russell) discloses the use of hydroxy- or amino-substituted carboxylic acids such as methyl salicylate, maleic acid, glycine, or dibutyl tartrate to inactivate metal catalyst residues. U.S. Pat. No. 4,452,932 (Brunelle) discloses the use of dehydroacetic acid and a hydroxy-aromatic compounds such as o-hydroxybenzophenone for inactivating metal catalyst residues. It also is known that certain polyols such as mannitol can be used to improve the color of polyester and polycarbonate blends as described in European Patent 0272417 (Nelson).
U.S. Pat. No. 4,619,956 discloses the combination of 2,2,6,6-tetraalkyl-piperidine hindered amine light stabilizers (HALS) and/or their addition salts with triazine ultraviolet absorbers for stabilizing thermoset acrylic and alkyd coatings. U.S. Pat. No. 5,714,530 discloses the utility of combining non-polymeric 2,2,6,6,-tetraalkylpiperidine HALS and/or their acid addition salts with triazine ultraviolet light absorbers for stabilizing certain polymer compositions. U.S. Pat. No. 6,051,164 discloses the use of a polymer stabilizing system comprising from about 50 to about 5,000 ppm of at least one ortho hydroxyl tris-aryl triazine light absorber and from about 500 ppm to about 1.25 percent of at least one oligomeric, polymeric or high molecular weight HALS having a molecular weight of at least about 500, wherein the weight ratio of HALS to triazine light absorber is from about 3:1 to about 20:1.
Certain of these phosphorus-containing compounds e.g., phosphoric acid, phosphorous acid, and polyphosphoric acid, can react with processing equipment to produce a dark colored polymer and can lead to the formation of black specks or particles. It is believed that the dark color is the due to corrosion of the process equipment. Addition of strong acids to the polymer compositions also reduces the hydrolytic stability as a result of acid catalyzed hydrolysis. Additionally, phosphite antioxidants can be hydrolyzed to acidic species thereby corroding process equipment or reducing the hydrolytic stability of the polymer composition. It is desirable to provide an additive or mixture of additives that can be used to deactivate metal catalyst residues and other metal impurities and thereby improve the color of polyester-polycarbonate compositions, reduce the corrosion of process equipment, and suppress transesterification.